1. Field of the Invention
The present invention relates to absorbent materials and their method of manufacture. Specifically, the present invention relates to absorbent materials formed from phycocolloids.
2. Description of the Related Art
The term "phycocolloid" refers to one of several carbohydrate polymers (polysaccharides) occurring in algae and moss. Phycocolloids are hydrophilic colloids having a tendency to absorb water and to form gels of varying strengths and consistency. The chief types of phycocolloids are carrageenan from Irish moss, algin from brown algae, and agar from red algae. Many uses for phycocolloids such as algin are known. The book titled Industrial Gums, Polysaccharides and Their Derivatives, edited by Roy L. Whistler (Academic Press, Second Edition, 1973), indicates that the use of algin is indicated whenever thickening, suspending, emulsifying, stabilizing, and gel-forming applications are involved. Algins are said to have found use in food products, pharmaceuticals and cosmetics, paper products, textile products, rubber products, and a number of other industrial uses.
The gel-forming properties of phycocolloids have resulted in the use of some phycocolloids in absorbent applications. U.S. Pat. No. 3,653,383 issued Apr. 4, 1972, to Wise describes an algin sponge. Disclosed is a water-absorbent and water-disintegrative open-celled porous algin sponge. The sponge is said to be useful as a medical receptor for biological fluids. The process of manufacture involves freezing an algin dispersion, such as a gel of sodium alginate and calcium alginate, and thereafter sublimating the frozen dispersion medium. Similarly, U.S. Pat. No. 4,090,013 issued May 16, 1978, to Ganslaw et al. is directed to an absorbent composition of matter. Described is a dry, water-swellable, water-insoluble absorbent composition of matter. The absorbent composition comprises an ionic complex of a water-soluble anionic polyelectrolyte and a polyvalent metal cation having a valence of at least 3. Naturally occurring polyelectrolytes which are suitable for forming the absorbent composition described by Ganslaw include anionic polyelectrolytes such as alginates, carrageenan, proteins, gum arabic, algin, agar, and gum ghatti.
The propensity of sodium alginate solutions to form spherical particles when dropped into a calcium chloride solution is known in the art of microencapsulation. See, for example, Biomedical Applications of Microencapsulation, Franklin Lim, Editor, (CRC Press, Inc., 1981) pp. 139-141; and Microcapsule Processing and Technology, Asaj Konda, (Marcel Dekker, Inc. 1979) pp. 59-63.
Unfortunately, known absorbent materials formed from phycocolloids have not proven particularly suited for use in the formation of absorbent products such as diapers, training pants, adult incontinence products, feminine care products, wound dressings and the like. As such, it is desirable to provide absorbent materials formed from phycocolloids which have a high degree of absorbency and which are suited for use in such absorbent products.